1. Field of the Invention
The present invention relates to a heat exchanger for a refrigerant cycle in which flammable fluid (i.e., flammable gas) such as propane or butane circulates as refrigerant.
2. Description of Related Art
An evaporator is one of heat exchangers disposed in a refrigerant cycle in which chlorofluorocarbon (hereinafter referred to as "flon") circulates as refrigerant. The evaporator has a plurality of tubes and tank portions which are formed by laminating and connecting a plurality of thin plates molded into predetermined shapes.
Recently, a refrigerant cycle in which flammable fluid such as propane or butane is used as refrigerant instead of flon has been widely studied. In such a refrigerant cycle, it is desired to use a heat exchanger which can prevent leakage of refrigerant (i.e, fluid) from the heat exchanger.
JP-A-58-120087 discloses a heat exchanger having a double-cylinder structure for detecting fluid leakage. However, the heat exchanger is designed for a hot-water supply system, and has a simple double-cylinder structure. That is, the heat exchanger is different from a laminated-type heat exchanger which is formed by laminating and connecting a plurality of thin plates. Therefore, the double-cylinder structure can not be directly applied to the laminated-type heat exchanger.